The present invention relates to a coupling designed to form a connection between elements and or details preferably of mechanical nature, at least one element or fitting having a principally cylindrical, or multifaced, outer surface.
In order to achieve a coupling of the above mentioned type, a number of various designs have previously been used. As examples of previously known connection members, intended to be used in connection with elements or pipe fittings having a cylindrical outer surface, can be mentioned couplings, including a cutting ring, which, in cooperation with a body member and a nut member, is brought to glide in a wedging manner along an embraced tubular element, thus forming a surrounding collar projecting upwardly from the outer peripheral portion of the tubular element. A securing and sealing joint is thus created, but plastic and mechanical deformation of the embraced tubular member is unavoidable. A further example of previously known joints for tubular elements are tube joints of DIN-type. These include a sealing ring with mainly conical cross-section soldered against the tubular element and arranged to compress a drawn copper washer against a seat when engaged by a screw member. The seat is arranged with a conical contact surface, against which the copper washer is deformed when the screw member is actuated. When a tightened joint is loosened, the sealing washer must be replaced by a new and nondeformed washer, before the joint can be retightened. As examples of previously known techniques can also be mentioned various types of soldering and welding joints. As a further example of a previously known coupling may be mentioned the type including a tubular connector having an external screw thread and being welded to a tubular member, which external screw thread is attachable to a flange member arranged with a corresponding internal screw thread. The flange member is in turn attached to a mechanical element by means of a bolt connection with an O-ring used as a sealing element between the flange member and a planar surface formed at the aforementioned mechanical element of fitting. The examples referred to above as prior art are mainly used for connection of tubular elements having a mainly cylindrical outer surface, but similar connector members are also used for connecting bars or axles having a generally cylindrical outer surface.
For connecting elements having a multifaced outer surface, it is previously known to use tubular elements preferably having a through recess, which in cross-section has a shape corresponding to the connected fitting. In order to achieve a locking effect between the tubular element and the embraced member, a screw means has often been utilized to press the embraced member against at least one inner surface of the tubular element. The tubular element has also often been arranged with a number of grooves and an outer surface adapted to interact with a preferably conical surface, e.g., arranged inside a nut member. A springy tubular member is thus achieved, which gradually reduces the area of the through recess when the nut member is rotated and thereby moved axially in relation to the tubular element, whereby an embraced element is locked by the tubular member under spring action.
A considerable disadvantage in respect of previously known types of joints is that they are not suitable for achieving a joint between e.g. a machinery part and a bar or tube-shaped element while maintaining a low height in a direction extending from the machinery part. A further disadvantage with previously known types of couplings is that they cannot be connected with maximum securing and sealing properties without risk of mechanical deformation of or damage to the connected fitting. A further important disadvantage is that, heretofore, it has been impossible to ascertain the force of securement caused by the joint, a feature most desirable in order to optimize the properties of the connected part in relation to tensile forces, internal pressure forces, etc. Furthermore, previously known joining members based on methods of attachment such as welding, mechanical deformation or other stress-creating methods, are eminently unsuitable when the joint is subjected to vibration forces, in which case rupture often has been the result.